The present invention relates to hardwired security systems and, in particular, to an integrated, time multiplexed, programmable alarm contact. Distinguishable binary programming and synchronizing/responding frequencies establish a unique alarm reporting interval and permit singular or redundant alarm status reports during successive reporting intervals.
The present invention relates to Applicant's pending U.S. Pat. No. 4,754,262 which discloses a time multiplexed security alarm system including a discrete micro-computer which is separately mounted in the vicinity of a plurality of distributed transponders and switch contacts. Each of the transponders have an assigned identity or reporting period relative to the reporting cycle of the micro-computer 10. Operating power for each transponder is derived from the hardwired transmission line coupling the transponders to the micro-computer 10.
The foregoing system also operates relative to narrow band tone signaling wherein a micro-computer directed synchronizing frequency, different from that of a transponder alarm frequency, induces transponder status transmissions. Each transponder's assigned transmission time is programmable by way of hardwired jumpers which require physical intervention by the installer. Also disclosed is a scheme including a counter for redundantly reporting contact openings.
A discussion of the operation of a related multiplexed module monitoring a plurality of input switches, wherein each switch has an assigned identity, in a micro-processor controlled security system may also be found upon directing attention to the present Assignee's copending U.S. Pat. application, Ser. No. 07/156,547 entitled "Micro-Programmable Security System."
Although the foregoing transponders and module provide numerous advantages to security system installers, heretofore the circuitry of each transponder has been separately mounted from the contact being monitored. It is preferable in many instances, however, that all of the associated transponder circuitry be integrated into a single package, along with the transponder switch typically a magnetically operated reed switch.
Such a package preferably should be small enough to be mounted in undetectable relation to the physical environmental condition being monitored. For example, the package should mount within a door or window frame and be obstructed by the monitored door or window, when in its normally aimed condition. Preferably, too, the circuit organization of such an assembly should permit performance of multiple and/or overlapped functions. Moreover, the transceiver circuitry should be responsive to a plurality of frequencies to permit improved system functionality.